Method for controlling a brushless electric motor

Abstract

The invention relates to a method for controlling a brushless electric motor for operation within a specified supply voltage range, a motor control controlling the winding voltage by means of pulse width modulation (PWM) and regulating the rotational speed to a specified speed. According to the invention, the motor is so rated that the nominal rotational speed is just achieved at the nominal operating point at the nominal supply voltage and at the maximum PWM ratio.

1. A method for controlling a brushless electric motor for operation within a specified supply voltage range, comprising:
 controlling the winding voltage by means of pulse width modulation (PWM) and regulating the rotational speed of the motor to a specified given value; 
 the motor being so rated that a nominal rotational speed is achieved at a nominal operating point at a nominal supply voltage and at a maximum PWM ratio; 
 if the supply voltage falls below the nominal voltage, operating the motor at the maximum PWM ratio; and 
 if the supply voltage exceeds the nominal voltage, regulating the rotational speed to the given value and causing the input power to the motor and the rotational speed to remain constant. 
 
   
   
     2. A method according to  claim 1 , wherein the rotational speed is derived from a commutation signal. 
   
   
     3. A method according to  claim 1 , wherein the motor rating is realized by an appropriate choice of winding wire diameter and number of windings. 
   
   
     4. A method according to  claim 2 , wherein the motor rating is realized by an appropriate choice of winding wire diameter and of the number of windings. 
   
   
     5. A brushless electric motor for operation within a specified voltage range, comprising:
 a motor control controlling winding voltage by means of pulse width modulation (PWM) and regulating rotational speed of the motor to a given maximum speed; 
 the motor being so rated that a nominal rotational speed is achieved at a nominal operating point at a nominal supply voltage and at a maximum PWM ratio; 
 if the supply voltage falls below the nominal voltage, the control operating the motor at the maximum PWM ratio; and 
 if the supply voltage exceeds the nominal voltage, the control regulating the rotational speed to the given value and causing input power to the motor and the rotational speed to remain constant. 
 
   
   
     6. A brushless electric motor according to  claim 5 , wherein the motor rating is realized by an appropriate choice of winding wire diameter and number of windings. 
   
   
     7. A brushless electric motor according to  claim 5 , wherein electronic commutation and closed-loop control are realized by means of a microcontroller. 
   
   
     8. A brushless electric motor according to  claim 5 , wherein the electric motor is a fan motor. 
   
   
     9. A brushless electric motor according to  claim 6 , wherein electronic communication and closed-loop control are realized by means of a microcontroller. 
   
   
     10. A brushless electric motor according to  claim 6 , wherein the electric motor is a fan motor. 
   
   
     11. A brushless electric motor according to  claim 7 , wherein the electric motor is a fan motor.